Machine vision system and method with multispectral light assembly

ABSTRACT

A multispectral light assembly for an illumination system includes a multispectral light source configured to generate a plurality of different wavelengths of light and a light pipe positioned in front of the multispectral light source and configured to provide color mixing for two or more of the plurality of different wavelengths. The multispectral light assembly also includes a diffusive surface on the light pipe and a projection lens positioned in front of the diffusive surface. A processor device may be in communication with the multispectral light assemblies and may be configured to control activation of the multispectral light source.

FIELD

The present disclosure relates generally to machine vision systems and,more particularly, to an illumination system with a plurality ofmultispectral light assemblies and a method for controlling themultispectral light assemblies.

BACKGROUND

Machine vision systems (also simply termed “vision systems”) use imageacquisition devices that include image sensors to deliver information ona viewed subject. The system can then interpret this informationaccording to a variety of algorithms to perform programmeddecision-making or identification functions. For example, an image of anobject containing features of interest to the system can be acquired byan on-board image sensor (also referred to as simply an “imager” or“sensor”) in the visible or near visible light range under appropriateillumination, which can be based upon ambient light or light provided byan internal or external illuminator.

Vision systems may be used for a variety of tasks in manufacturing,logistics and industry. A common task for vision systems is the readingand decoding of symbology (e.g., one-dimensional and two-dimensionalcodes—also termed “IDs”), which are used in a wide variety ofapplications and industries and can take the form of ID barcodes, 2DDataMatrix Codes, QR Codes and Dot-Codes, among other. The image sensoracquires images (typically grayscale or color, and in one, two, or threedimensions) of the subject or object, and processes these acquiredimages using an on-board or interconnected vision system processor. Theprocessor often includes both processing hardware and non-transitorycomputer-readable program instructions (software) that perform one ormore vision system processes to generate a desired output based upon theimage's processed information. This image information is typicallyprovided within an array of image pixels each having various colors orintensities. In the example of an ID reader (also termed herein, a“reader”), the user or an automated process acquires an image of anobject that is believed to contain one or more barcodes, 2D codes orother ID types. The image is processed to identify encoded features,which are then decoded by a decoding process or processes to obtain theinherent alphanumeric data represented by the code.

Vision systems may also be used for other tasks such as, for example,surface and parts inspection, alignment of objects during assembly,measurement, and any other operations in which visual data is acquiredand interpreted for use in further processes. For example, a visionsystem may be used to inspect objects (e.g., components or parts) on aproduction line (e.g., during manufacturing processes) to ensure thatthe objects meet predefined criteria. For example, each object may beexpected to contain certain features or characteristics. In aninspection process, the image sensor of the vision system may acquireimages of an object and the images may be processed (e.g., using avision system processor) to identify features or characteristics of theobject. The results of the inspection process may be provided to adisplay for viewing by an operator. If the object passes the inspection,the object may be kept on the production line for further processingand/or handling. If the object fails the inspection, the object may bemarked and/or removed from the production line.

SUMMARY

In accordance with an embodiment, an illumination assembly for a machinevision system includes a plurality of multispectral light assemblies.Each multispectral light assembly includes a multispectral light sourceconfigured to generate a plurality of different wavelengths of light anda light pipe having an entrance surface and an exit surface andpositioned in front of the multispectral light source. The light pipe isconfigured to receive two or more of the plurality of differentwavelengths of light generated by the multispectral light source and toprovide color mixing for the two or more of the plurality of differentwavelengths of light. The multispectral light assembly also includes adiffusive surface on the exit surface of the light pipe and configuredto receive color-mixed light transmitted from the light pipe and aprojection lens positioned in front of the diffusive surface andconfigured to receive the color-mixed light from the diffusive surfaceand to project a light beam onto an object that includes the color-mixedlight. The illumination assembly also includes a processor device thatis in communication with the plurality of multispectral lightassemblies. The processor device is configured to control activation ofthe multispectral light source of each of the plurality of multispectrallight assemblies.

In some embodiments, an illumination assembly can include amultispectral light source that includes a plurality of color lightemitting diodes (LEDs), configured to separately provide differentrespective wavelengths of light. In some embodiments, an illuminationassembly can include a multispectral light source that includes an RGBWLED, an RGB IR LED, or an RGBY LED. In some embodiments, an illuminationassembly can include an illumination sensor that can be in communicationwith the processor device and configured to receive at least onewavelength of light generated by the multispectral light source andmeasure the intensity of the wavelength of light. In some embodiments,an illumination assembly can include a processor device that can beconfigured to receive the measured intensity of at least one wavelengthof light and one or more of adjust the intensity of the at least onewavelength of light or adjust an exposure time for the at least onewavelength of light, based on the measured intensity. In someembodiments, an illumination assembly can include a processor device thecan be configured to adjust the intensity of the at least one wavelengthof light based on comparing the measured intensity to a targetintensity. In some embodiments, an illumination assembly can include adiffusive surface that is configured to control an angle of the lighttransmitted from a light pipe. In some embodiments, an illuminationassembly can include a diffusive surface that can be configured tocontrol the shape of the light transmitted from a light pipe. In someembodiments, an illumination assembly can include a projection lens thatis one of an aspherical shaped lens, a spherical shaped lens, a toroidalshaped lens, a cylindrical shaped lens, a freeform shaped lens, or acombination of different lens shapes. In some embodiments, the lightbeam projected onto the object may have a shape approximately equal to ashape of a field of view (FOV) of the machine vision system. In someembodiments, the light beam projected onto the object has a rectangularshape. In some embodiments, the diffusive surface is a diffusing textureon the exit surface of the light pipe. In some embodiments, a shape ofthe light pipe and a ratio between an area of the entrance surface andthe exit surface of the light pipe are optimized for color mixing.

In accordance with another embodiment, a machine vision system includesan optics assembly with at least one lens, a sensor assembly includingan image sensor and an illumination assembly comprising a plurality ofmultispectral light assemblies positioned symmetrically around the atleast one lens. Each multispectral light assembly includes amultispectral light source having a plurality of color LED dies. Each ofthe plurality of color LED dies is configured to generate a differentwavelength of light. An orientation of the plurality of color LED diesis configured to provide a balanced distribution of color in anillumination area. The multispectral light assembly further includes alight pipe positioned in front of the multispectral light source andhaving an exit surface, a diffusive surface on the exit surface of thelight pipe, and a projection lens positioned in front of the diffusivesurface and configured to project the illumination area onto an object.The machine visions system further includes a processor device incommunication with the optics assembly, the sensor assembly and theillumination assembly. The processor device is configured to controlactivation of each of the plurality of color LED dies.

In some embodiments, a machine vision system can include a processordevice that can be configured to activate each of a plurality of colorLED dies in a multispectral light source sequentially. In someembodiments, a machine vision system can include a processor device thatcan be configured to activate each of a plurality of color LED dies in amultispectral light source sequentially during a single exposure time.In some embodiments, a machine vision system can include a housingdisposed around an optics assembly, a sensor assembly, an illuminationassembly and a processor device, and can include a diffused lightassembly removably attached to the housing in front of the illuminationassembly, the diffused light assembly configured to convert lighttransmitted from the illumination assembly to a diffuse light. In someembodiments, a machine visions system can include a multispectral lightsource that includes a plurality of color LED dies and each LED dies ofthe plurality of color LED dies includes a plurality of lightingpositions, with each light position of the plurality of lightingpositions for each LED die of the plurality of color dies includes anLED of a different respective color and the plurality of multispectrallight assemblies collectively include an equal number of differentrespective colors in each of the plurality of lighting positions.

In accordance with another embodiment, a method for controlling anillumination system for a machine vision system used to acquire an imageof a symbol on an object includes projecting, using at least onemultispectral light source and a corresponding light pipe, a first lightbeam for a first period of time. The first light beam has a firstwavelength associated with a first color channel. The method furtherincludes measuring, using an illumination sensor, an intensity of thefirst light beam, comparing, using a processor device, the measuredintensity of the first light beam to a first target intensity,adjusting, using the processor device, an amount of light for the firstlight beam based on the comparison of the measured intensity of thefirst light beam and the target intensity and repeating adjusting theamount of light until the measured intensity of the first light beam isequal to the target intensity. After the first period of time, themethod further includes projecting, using the at least one multispectrallight source and a corresponding light pipe, a second light beam for asecond period of time. The second light beam has a second wavelengthassociated with a second color channel. The method further includesmeasuring, using the illumination sensor, an intensity of the secondlight beam, comparing, using the processor device, the measuredintensity of the second light beam to a second target intensity,adjusting, using the processor device, an amount of light for the secondlight beam based on the comparison of the measured intensity of thesecond light beam and the second target intensity, and repeatingadjusting the amount of light until the measured intensity of the secondlight beam is equal to the second target intensity.

In some embodiments, a method for controlling an illumination system fora machine vision system can include projecting a first light beam and asecond light beam sequentially. In some embodiments, a method forcontrolling an illumination system for a machine vision system caninclude projecting a first light beam for a first period of time andprojecting a second light beam for a second period of time and the firstperiod of time and the second period of time can be within one exposuretime. In some embodiments, a method for controlling an illuminationsystem for a machine vision system can include adjusting an amount oflight for a first light beam or a second light beam including adjustingthe duration of the first period of time or the second period of time.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will hereafter be described with reference to theaccompanying drawings, wherein like reference numerals denote likeelements.

FIG. 1 is a schematic diagram of a multispectral light assembly inaccordance with an embodiment of the technology;

FIG. 2 is a schematic block diagram of vision system with a plurality ofmultispectral light assemblies in accordance with an embodiment of thetechnology;

FIG. 3 is a diagram illustrating an example orientation of a pluralityof multispectral light sources for an illumination system in accordancewith an embodiment of the technology;

FIG. 4 illustrates example illumination light patterns generated usingvarious combinations of illumination from multispectral light assembliesin an illumination system in accordance with an embodiment of thetechnology;

FIG. 5 is a schematic diagram showing example light bankingconfigurations of an illumination system in accordance with anembodiment of the technology;

FIG. 6 illustrates a method for controlling an illumination system withmultispectral light assemblies for generating an image in accordancewith an embodiment of the technology;

FIG. 7 is a graph illustrating a timing configuration using multipleexposures for generating an image using an illumination system withmultispectral light assemblies in accordance with an embodiment of thetechnology;

FIG. 8 is a graph illustrating a timing configuration using a singleexposure for generating an image using an illumination system withmultispectral light assemblies in accordance with an embodiment of thetechnology;

FIG. 9 illustrates an example diffused light assembly in accordance withan embodiment of the technology; and

FIG. 10 is a schematic block diagram of a vision system and the diffusedlight assembly of FIG. 9 in accordance with an embodiment of thetechnology.

DETAILED DESCRIPTION

Visions systems may be used in a variety of applications includingreading and decoding IDs (e.g., barcodes), inspecting objects andsurfaces, alignment of objects during assembly, measurement, and anyother operations in which visual data is acquired and interpreted foruse in further processes. ID (e.g., barcode) readers are generallyconfigured to track and sort objects, including along a line (e.g., aconveyor) in manufacturing and logistics operations. The ID reader, ormore typically, a plurality (constellation) of readers can be positionedover the line (or otherwise) at an appropriate viewing angle(s) toacquire any expected ID codes on the face(s) of respective objects asthey each move through the field of view. The ID reader can also beprovided in a handheld configuration that allows the user to move fromobject to object, for example, on an inspection floor and vary thedistance or relative angle between the reader and object surface atwill. More generally, the focus distance of the ID reader with respectto the object can vary, depending on the placement of the reader withrespect to the line and the size of the object. Visions systems forinspection are generally configured to capture an image of an object(e.g., a component or part) on a production or assembly line, processingthe image to determine if the object meets a predefined criteria (e.g.,one or more expected features are present), and report the inspectionresults. Such machine vision systems may aid in the inspection,assembly, and/or handling of various types of articles, parts, anddevices, including automotive parts (e.g., fuses, gaskets, and sparkplugs), electrical components (e.g., connector pins, keyboards, LED, LCDdisplays), medical and pharmaceutical products (e.g., disposable testkits, syringes, needles, and date-lot codes), and consumer products(e.g., razor blades and floppy disks).

In operation, some vision systems (e.g., ID readers or inspectionsystems) or associated lighting attachments function to illuminate thescene containing one or more objects (e.g., ID's, components or parts).For an ID reader, this illumination can include aimers that project acolored dot on the region of interest in the imaged scene, whereby theuser can center the image axis of the reader on the barcode within theimaged scene. Illumination for a vision system can also include generalillumination to allow acquisition of appropriately detailed images. Theilluminated scene is then acquired by an image sensor within the imagingsystem through optics. The array of pixels of the sensor is exposed, andthe electronic value(s) generated for each pixel by the exposure is/arestored in an array of memory cells, as can be termed the “image” of thescene. In the context of an ID-reading application, the scene caninclude an object of interest that has one or more IDs of appropriatedimensions and type (e.g., DPM codes, printed barcodes, etc.). The ID(s)are part of the stored image. In the context of an inspection system,the scene can include an area encompassing all pertinent portions of theobject of interest in the field of view and the area around the objectof interest.

Vision systems may utilize multispectral light sources for illuminationof an object for various applications where color (or othermulti-wavelength) images are advantageous. As used herein, amultispectral light source is a light source that can separatelygenerate a plurality of different wavelengths of light (e.g., a lightsource assembly that includes a plurality of distinct lightsub-assemblies, each of which can generate a different respectivewavelength peak or band. For example, multispectral light sources suchas red, green, blue, yellow, infrared (IR), or ultraviolet (UV) lightemitting diodes (LEDs) may be used in a vision system to providemultispectral capabilities.

Many conventional systems with multispectral light sources use adiffuser (e.g., a Lambertian diffuser) with the multispectral lightsource. A diffuser typically may be formed from a sheet of milky whiteand transparent material that completely diffuses the light in alldirections, such that the light projected generally toward an imagingarea may be spread out almost 180°. This can result in a more intensecore illumination, with the intensity of light dropping off at largerangles. Despite this effect, a diffuser can generally spread out thelight over an area with relatively uniform light distribution and cansometimes be used to provide relatively good color mixing uniformity,however, a diffuser increases the physical size and the etendue of thesystem which can significantly reduce the efficiency. As a result, theworking distance of multispectral lights which use a diffuser is usuallyshort (e.g., 0.3 m maximum). The loss of light from a diffuser alsomakes it difficult to use with different light banks. In addition,conventional systems with multispectral capabilities may require a largenumber (e.g., 80-100) of monochromatic LED's for each wavelength (i.e.,each color). Further, to achieve color uniformity, many conventionalsystems illuminate using the different LEDs simultaneously withdifferent intensities.

Among other aspects, the present disclosure describes a vision system(and related method) that includes a compact illumination assemblyhaving a plurality of multispectral light assemblies that can be used toproject direct light (e.g., color mixed) into a well-defined andrelatively uniformly illuminated area. For example, each multispectrallight assembly of a plurality of light assemblies can include amultispectral light source with a plurality of LEDs with differentwavelengths, and a light pipe. In some embodiments, a multispectrallight assembly can further include one or more of a diffusive surface ora projection lens. In an embodiment, the multispectral light sourceincludes various color LED dies in a single package which can reduce thenumber of LEDs in the illumination system. For example, in someembodiments the multispectral light source may be a RGB LED, an RGBWLED, a RGB(IR) LED, an RGBY LED or other RGB or multi-wavelength LEDtype.

Advantageously, in some embodiments, a light pipe in a multispectrallight assembly can enable color mixing of a plurality of colors,homogenize the different spectrums, and correct for non-uniformitycaused by off-axis placement of the different color dies in themultispectral light source. As a further advantage, the multispectrallight assemblies can generally generate more direct light (rather thandiffuse) at longer distances. For example, in an embodiment, thedisclosed multispectral light assembly may be used in a vision system toacquire images of an object at up to 1.0 m working distance. In someembodiments, the light from the multispectral light assembly may beprojected efficiently in a rectangular area that has a shape that isapproximately equal to the field of view (FOV) of the camera of thevision system (e.g., is rectangular for a rectangular FOV, with orwithout rounded, chamfered, or otherwise truncated corners, and with anaspect ratio that is within 5%, 10%, or 20% of the aspect ratio of theFOV). In some embodiments, the light from the multispectral lightassembly may be projected in areas with other shapes such as a square.Advantageously, a vision system incorporating one or more of themultispectral light assemblies may provide direct color mixed lightusing the one or more multispectral light assemblies allowing for anextended working range with the minimum number of multispectral lightsources.

In another aspect, the present disclosure describes an optimizedorientation of the LED dies in the multispectral light assemblies toprovide balance and symmetry between quadrants of the light projected bythe illumination system, for example, to provide similar intensity atthe center and the edges of the illumination area. The optimizedorientation can also be designed based on desired size and spaceconstraints for the vision system. A further advantage of the disclosedsystem is that the multispectral light assemblies in the illuminationassembly may be positioned in banks symmetrically around the lens of thevision system. Advantageously, this can enable the system to be used forvision system applications that require directed light from differentdirections. In some embodiments, the improved LED orientation or theimproved bank arrangements can be used with multispectral lightassemblies, including as generally described above.

In yet another aspect, the present disclosure describes a method forcontrolling the amount of light from the different color channels of theillumination assembly using an illumination sensor and a feedback loop.Advantageously, in some implementations, the method can activate theseparate colors sequentially and, therefore, only one color channel at atime needs to be measured by the illumination sensor and adjusted toachieve a target intensity. Accordingly, in some embodiments, therequired hardware for the feedback loop may be simpler: for example, asingle photo diode may be used for the illumination sensor since onlyone color channel is activated and measured at a time. In someembodiments, each color channel may be activated sequentially during asingle exposure. In other embodiments, each color channel is activatedduring a separate exposure and each color channel exposure may beimplemented sequentially.

FIG. 1 is a schematic block diagram of a multispectral light assembly inaccordance with an embodiment of the technology. In some embodiments, aplurality of multispectral light assemblies 100 may be used in anillumination assembly of a vision system as discussed further below. Inthe embodiment shown in FIG. 1 , the multispectral light assembly 100includes a multispectral light source 102 and beam shaping optics 116that include a light pipe 104, a diffusive surface 106 and a projectionlens 108.

Multispectral light source 102 can include a plurality of color LED diesthat generate light in multiple wavelengths. In an embodiment, theplurality of color LED dies can be provided in a single package, forexample, a RGB LED, an RGBW LED, a RGB(IR) LED, an RGBY LED or other RGBLED type. Each LED die of the multispectral light source may becontrolled independently (e.g., using a processor). In some embodiments,the multispectral light source may be an RGBW LED. An RGBW LED may beadvantageous for certain applications, for example, for applicationssuch as ID (e.g., barcode) reading when a flashing color of light is notdesirable. In addition, the white LED may advantageously be used toincrease the number of color channels that may be provided by themultispectral light source 102. For example, a filter may be placed ontop of the white LED die of the RGBW LED package to provide the desiredadditional color. Alternatively, in other embodiments, a multispectrallight with the additional desired color LED die may be used, forexample, an RGBY LED, an RGB(IR) LED, an RGB(UV) LED, etc.

In the embodiment of FIG. 1 , the light pipe 104 is positioned in frontof the multispectral light source 102, along an illumination direction,and behind the diffusive surface 106 and the projection lens 108. Thelight pipe 104 has a length 110, an entrance surface 112 disposedproximate to the multispectral light source 102, and an exit surface114. In some embodiments, the shape of the light pipe 104 (asillustrated in FIG. 1 ) may be an inverted truncated pyramid or asimilar geometry. In some embodiments, the length 110 of the light pipe104 and a ratio between the area of the entrance 112 and exit 114surfaces can be optimized to obtain good color mixing with compactdimensions, including over a relatively short dimension in theillumination direction, as compared to conventional systems. In someembodiments, the geometry or shape of the edges of the light pipe 104may be optimized. In some embodiments, the entrance 112 and exit 114surfaces of the light pipe 104 may have a curved geometry. In someembodiments, the shape of the light pipe 104 may be a curved truncatedpyramid. In some embodiments, the shape of the light pipe 104 may notfollow a particular defined shape, for example, the shape of the lightpipe 104 may be a freeform curve.

Generally, the light pipe 104 can be used to collect the maximum amountof light from the multispectral light source 102. In addition, the lightpipe 104 can provide a square surface to project the light in arectangular area and may be used to correct for non-uniformity caused byoff-axis placement of the different color dies of the multispectrallight source 102. In some embodiments, the light from the light pipe 104may be projected in areas with other shapes such as a square.Advantageously, the light pipe 104 is configured to provide color mixingincluding the combination of multiple colors. Light pipe 104 can be usedto homogenize the different spectrums generated by the multispectrallight source 102 and also to make the mixing of color more uniform. Afurther advantage of using a light pipe 104 is that the light pipe 104can enable the projection of direct light (e.g., color mixed) at longerworking distances. In some embodiments, the light pipe enables theprojection of light in a rectangular area that has a shape that isapproximately equal to the field of view (FOV) of a camera of a visionsystem. As shown in FIG. 1 , each multispectral light assembly 100 mayinclude a light pipe 104. Accordingly, in a vision system with aplurality of multispectral light assemblies 100, each multispectrallight assembly may include a light pipe 104. In alternative embodiments,a plurality of light pipes may be provided independently, for example, aplurality light pipes may be provided as a separate unitary structurewhere the light pipes are connected or coupled to each other. The lightpipe structure may be removably coupled to a plurality of multispectrallight assemblies. For example an independent light pipe structure may beprovided with four light pipes with four connections between the lightpipes. In some embodiments, the number of light pipes in the separate,independent light pipe structure may fewer than the number ofmultispectral light sources in the vision system.

In some embodiments, the diffusive surface 106 may be, for example, aholographic diffuser positioned on the exit surface 114 of the lightpipe 104, a diffusing pattern or texture (e.g., roughness) applied tothe exit surface 114 of the light pipe 104, or a micro lenses array(MLA) in the form of foils with adhesive that may be installed on theexit surface 114 of the light pipe 104. For example, in someembodiments, the diffusive surface 106 may be formed by a holographicdiffuser that may be attached to the light pipe 104 during a moldingprocess of the light pipe 104 or may be attached to the light pipe 104after the molding process of the light pipe 104. In another example, thediffusive surface 106 may be formed by a diffusive pattern or textureapplied to the exit surface 114 of the light pipe or a diffusive patternor texture may be formed with the light pipe 104 as one unitary piece.The diffusive surface 106 may be used to control of the shape of atransmitted light beam from the light pipe 104 and to control the angleof the light beam coming out of the light pipe 104. The diffusivesurface 106 can be used to make the light pattern at the exit surface114 of the light pipe 104 more uniform and to provide an optimizedbalance between uniformity and efficiency between the light pipe 106 andthe projection lens 108, with noted improvement in uniformity andefficiency relative to conventional (e.g., Lambertian) diffusers.Accordingly, the diffusive surface 106 can be used to both improve andbalance the efficiency and uniformity of the light pattern projectedfrom the light pipe 104. In addition, the light pipe 104 and diffusivesurface 106 may be used together to achieve advantageous color mixingproperties for the different wavelengths traveling through them, with avery compact size. Advantageously, the diffusive surface 106 may be usedto overcome limitations on the length of the light pipe 104, forexample, the optimal length of the light pipe 104 may be too large forthe overall size constraints of a vision system resulting in the use ofa smaller length light pipe. In some embodiments, if there is enoughspace in the vision system for a light pipe with an optimal length, theexit surface 114 of the light pipe 104 may be clear or transparentwithout a diffusive surface.

As also shown in the embodiment of FIG. 1 , the projection lens 108 maybe positioned in front of the light pipe 104 and diffusive surface 106.In an embodiment, the projection lens 108 can finally project thediffusive surface 106 on to the target area. In some embodiments, tofurther reduce the size of the multispectral light assembly 100 (and theoverall size of the vision system) the projection lens 108 may be formedwith a high refractive index. In addition, the size of the projectionlens 108 may also be minimized by using an aspherical shaped lens. Insome embodiments, the projection lens 108 may be a lens with a freeformshaped geometry. Advantageously, a freeform sharped geometry lens canallow for the modification of a light beam in every single point. Insome embodiments, different shaped lenses may also be used for theprojection lens 108 including, but not limited to, a spherical geometry,a Toroidal geometry, a cylindrical geometry and/or a combination ofdifferent geometries in a single lens. As mentioned above, themultispectral light assembly 100 may be configured to generate anillumination area shape that is approximately equal to the FOV of acamera of a vision system that includes the multispectral light assembly100. For example, the light from the multispectral light assembly 100may be projected efficiently in a rectangular area that follows the coneof the FOV rather than a random rectangle or round profile. In someembodiments, the light from the multispectral light assembly 100 may beprojected in areas with other shapes such as a square.

In an embodiment, the combination the light pipe 104 and an asphericalprojection lens 108 can allow for effectively imaging the exit 114 ofthe light pipe 104 onto the target (e.g., a rectangular illuminationarea). Advantageously, the combination of the light pipe 104, diffusivesurface 106 and projection lens 108 can enable uniform color mixing withcompact dimensions of the beam shaping optics 116. In some embodiments,the total track of the multispectral light assembly from themultispectral light source 102 to the vertex of the projection lens 108may be about 25 mm. In some embodiments, the total track of themultispectral light assembly from the multispectral light source 102 tothe vertex of the projection lens may be larger or smaller than 25 mm.In addition, the combination of the light pipe 104, diffusive surface106 and projection lens 108 can enable a longer working distance andmore directed light. In some embodiments, the light distribution andcolor mixing in the projected illumination area of the multispectrallight assembly 100 may be configured for a working distance of 300-1000mm. In some embodiments, the light distribution and color mixing in theprojected illumination area of the multispectral light assembly 100 maybe configured for a working distance less than 300 mm or greater than1000 mm. Accordingly, various embodiments of the multispectral lightassembly 100 may advantageously be used for a wide range of differentworking distances. In some examples, the working distance may be 100-300mm, 300-500 mm, 800-1000 mm, or 1000-1200 mm. Although the illustratedarrangement of the multispectral light assembly 100 can be advantageous,including for reasons discussed above, other configurations are alsopossible, including configurations in which one or more of the lightpipe 104, the diffusive surface 106, or the projection lens 108 aredifferently configured, differently arranged, or omitted.

As mentioned above, a plurality of multispectral light assemblies (e.g.,of the multispectral light assemblies 100) may be used in anillumination system of a vision system. FIG. 2 is a schematic blockdiagram of vision system 200 with a plurality of multispectral lightassemblies in accordance with an embodiment of the technology. WhileFIG. 2 illustrates an embodiment of a vision system arrangement, itshould be understood that the various embodiments described herein maybe implemented on different types of vision systems including, but notlimited to, mobile (e.g., hand held) or fixed mount ID readers,inspection systems, etc. It should be noted that the depictedarrangement of components is illustrative of a wide range of layouts andcomponent types. The illustrated embodiment is thus provided to teach apossible arrangement of components that provide the functions of theillustrative embodiment, although other embodiments can exhibit otherconfigurations.

The vision system 200 shown in FIG. 2 includes an illumination assembly214, and a vision camera assembly 224 that includes an image sensor 204and an optics assembly 206. The vision system 200 can be used to acquirean image of an object 210 or an exemplary ID (e.g., a barcode) 211 onthe object 210. The vision system 200 also includes processingcomponents (e.g., processor 202) that perform various vision systemtasks such as ID code finding and decoding, inspection, etc. Theillumination assembly 214 may include a plurality of multispectral lightassemblies 216, 218, 220. Each of the multispectral light assemblies216, 218, 220 may be, for example, an identical or varied implementationof the multispectral light assembly 100 as described above with respectto FIG. 1 . While three multispectral light assemblies are shown, itshould be understood that different numbers of multispectral lightassemblies may be used in the illumination assembly 214 in otherembodiments (e.g., two, four, eight, sixteen, etc.).

As described above relative to the assembly 100, for example, eachmultispectral light assembly 216, 218, 220 can include a multispectrallight source, a light pipe, a diffusive surface and a projection lens108. The plurality of multispectral light assemblies 216, 218, 220 inthe illumination assembly 214 may be used to generate light in multiplewavelengths that may be projected onto the object 210 to, for example,acquire an image of the object 210 or an image or the ID 212 on theobject. As discussed further below, in some embodiments, differentwavelengths (i.e., color channels) can be activated sequentially oraccording to other control strategies.

In some embodiments, the plurality of multispectral light assemblies216, 218, 220 are positioned symmetrically around the camera lens (e.g.,lens(es) 208 of the optics assembly 206). For example, light assembliesor banks of light assemblies can be distributed at regular intervalsaround a lens or in a balanced configuration on multiple sides of alens. In addition, the orientation of the color LED dies of themultispectral light source in each multispectral light assembly may bearranged to provide the desired uniformity, including as furtherdiscussed below. The illumination assembly 214 may advantageously beused to project direct light (e.g., color mixed) into a well-defined anduniformly illuminated area on the object 210, for example, anilluminated area that has a shape that is approximately equal to thefield of view (FOV) of the vision camera 224. In some embodiments, theilluminated area may be a rectangular area. In some embodiments, theilluminated area may have other shapes such as a square.

As mentioned, the vision system 200 can be used to acquire an image ofthe object 210 or the exemplary ID 212, for example, in the form of abarcode, on the object 210. An image may be acquired by projecting anillumination light on the object 210 and receiving reflectedillumination light from the object 210. Thus, in front of the imagesensor 204 is placed an optics assembly 206 having a series of lenses208 that project the images light onto the area of the image sensor 204and, correspondingly, define a FOV for imaging with the image sensor204. In an embodiment, the optics assembly 206 may include one or moreliquid lenses, as may allow for rapid and automated adjustment of focusfor images at different working distances. In other embodiments, theoptics assembly 206 can include a lens assembly 208 with mechanicalparts (e.g., gear, motor and thread assembly) that are used to move alens toward or away from the image sensor 204 to change the focaldistance of the system 200 Light projected from the illuminationassembly 214 that is reflected from the object 210 back to the visionsystem 200 is directed through the lens(es) 208 along a reader opticalaxis OA to the image sensor 204. The image sensor 204 can be configuredto detect different wavelengths of light. In some embodiments, the imagesensor 204 may be monochromatic sensor (e.g., black and white) or acolor sensor. The reflected light is received by the image sensor 204for processing (e.g., by processor 202) to, for example, generate animage of the subject. Known methods may be used for generating an imageof the scene and decoding data therein.

The processor 202 can control vision system analysis processes (e.g., IDreading and decoding, inspection) as well as other functions, includingprojection of an aimer beam, illumination for image acquisition (e.g.,timing or intensity of illumination, selection of a light source forillumination, etc.), automatic focus adjustment, etc. In someembodiments, the processor 202 can include one or more processor devicesthat can be provided on one or more circuit boards and operativelyinterconnected by the appropriate ribbon cable(s) or other communicationchannels (not shown). The system 200 may also be configured towirelessly transmit (via a wireless link, not shown) decoded data to adata handling device such as an inventory tracking computer or logisticsapplication. Alternatively, the system 200 may be wired to a datahandling device/network or can store and subsequently transfer collectedinformation when it is connected to a base unit. The processor 202 maybe in communication with the image sensor 204, the illumination assembly214, as well as a variety of other components (not shown), such asmotors for an adjustment of system orientation, or a variety of otheractuators.

In some embodiments, the vision system 200 also includes an integrated(e.g., internal) illumination sensor 222 that is in communication withthe processor and, for example, located proximate to the multispectrallight assemblies 216, 218, 220 of the illuminations assembly 214. In anembodiment, the illumination sensor 22 may be integrated into theillumination assembly 214. The illumination sensor 222 and the processor202 can implement a feedback loop that may be used to control the amountof light of the different color channels projected by the illuminationassembly 214 and thereby improve image acquisition. In some embodiments,the illumination sensor 222 may advantageously be located proximate toor near the multispectral LEDs in the vision system 200. For example,the illumination sensor 222 may be located at a PCB level (printedcircuit board) of the vision system 200 and collect light from the LEDsof the multispectral light assemblies 216, 218, 220. In someembodiments, a plurality of illumination sensors 222 may be locatedhigher in the structure of the vision system 200, for example, proximateto or near the lenses (e.g., lens 108) of each multispectral lightassembly 216, 218, 220 and a far end of the vision system 200. In thisembodiment, it is advantageous to include a plurality of illuminationsensors 222 because it may be possible that not all of the subsystems ofthe vision system 200 may perform with the same efficiency. Theillumination sensors 222 can be coupled to the PCB of the vision system200 and located at a particular height.

For example, as also discussed further below, part of the lighttransmitted through one or more light pipes of one more multispectrallight assemblies 216, 218, 220 can be diverted onto, or otherwisereceived by, the illumination sensor 222, which can then measure theintensity of the light. As appropriate, the measured intensity can beused to control the amount of light (intensity and/or LED on-time) foreach of the wavelengths (a.k.a. color channels).

Advantageously, in some embodiments, each wavelength or color channel isactivated sequentially so that only one channel is on (i.e.,illuminating a target for imaging) at any time. Accordingly, theillumination sensor 214 only needs to measure one color channel at atime and the illumination sensor 222 may be, for example, a singlephoto-diode that may be used to measure each of the colors. As eachcolor channel is on, the intensity or an exposure time can be adjusteduntil a target amount of light or exposure (i.e., the product of theintensity and exposure duration (or exposure time or LED on-time)) isreached. Once the target exposure (or amount of light) is reached for aparticular color channel, the channel can be turned off, and the nextcolor channel can be turned on (as appropriate). In an embodiment, thefeedback loop and exposure adjustment may be repeated for each colorchannel as each channel is sequentially activated.

In some embodiments, each wavelength or color channel may be activatedsimultaneously so that all channels are on (i.e., illuminating a targetfor imaging) at the same time. Accordingly, in some embodiments, theilluminations sensor 222 may include a plurality of illumination sensorsand each illumination sensor may be configured to measure one of thecolor channels. For example, each illumination sensor 222 may be, forexample, a photodiode configured to measure one of the colors. In someembodiments, for simultaneous illumination with a plurality of colorschannels, the illumination sensor 222 may be a single illuminationsensor 222 (e.g., a photodiode) configured to measure all of the colorchannels simultaneously. In some embodiments with simultaneousactivation of each wavelength or color channel, color mixing may beperformed and colors beyond those installed on a system (e.g., thesystem shown in FIG. 2 ) may be measured. As mentioned above, theintensity or an exposure time of each color channel can be adjusteduntil a target amount of light or exposure (i.e., the product of theintensity and exposure duration (or exposure time or LED on-time)) isreached. Once the target exposure (or amount of light) is reached for aparticular color channel, the channel can be turned off.

As mentioned above, the orientation of the color LED dies of themultispectral light source in each multispectral light assembly may bearranged to provide the desired uniformity. In some embodiments, each ofthe color LED dies can include multiple lighting positions (e.g., in aquadrant arrangement), and a beneficial lighting uniformity can beobtained by collectively balancing the distribution of illuminationsources for particular colors relative to lighting positions in each ofthe multispectral light sources. For example, where each multispectrallight source of a plurality of multispectral light sources includes aplurality of light positions, with a common spatial arrangement, thesame number of LEDs of a particular color can be provided in each of thelight positions, when all of the light positions of the pluralitymultispectral light sources are considered collectively.

Further in this regard, for example, FIG. 3 is a diagram illustrating anexample orientation of a plurality of multispectral light sources for anillumination system in accordance with an embodiment of the technology.In this example, eight multispectral light sources 310, 312, 314, 316,318, 320, 322 and 324 are shown, however, in other embodiments, theillumination assembly may comprises different numbers of multispectrallight sources (and the associated multispectral light assemblies). Inthe illustrated embodiment of FIG. 3 , each multispectral light source310-324 is a RGBW LED, however, it should be understood that othermultispectral LEDs may be used, for example, RGB, RGB(IR), RGBY,RGB(UV), etc. Each multispectral light source 310-324 contains one eachof the color LED dies Red (R) 326, Green (G) 328, Blue (B) 330 and White(W) 332. The color LED dies 326-332 of each RGBW LED 310-324 areoff-axis and, therefore, it is advantageous to provide the dies in anorientation that is as symmetric as possible to provide the desireduniformity. In the example orientation shown in FIG. 3 , the light fromthe illumination assembly is divided into four quadrants, namely a firstquadrant 302, a second quadrant 304, a third quadrant 306 and a fourthquadrant 308. Considering the lighting array collectively, two of theeight RGBW LEDS 310-324 are positioned in each quadrant 302-308 so as tobe symmetrically positioned around a camera axis. Namely, RGBW LEDs 310and 312 are located in the first quadrat 302, RGBW LEDs 3114 and 316 arelocated in the second quadrant 304, RGBW LEDs 318 and 320 are located inthe third quadrant 306 and RGBW LEDs 322 and 324 are located in thefourth quadrant 308. In another embodiment with 16 RGBW LEDs, four RGBWLEDS would be positioned in each quadrant.

Further, in the illustrated example, each color LED die 326-332 ispresent in the same position and orientation (i.e., in the same lightingposition for the given LED die) two times, as indicated by the dashedline arrows, to provide a balanced distribution of color. Although avariety of approaches can provide this result, in the illustratedexample, the color LED die orientation is the same for RGBW LED 310 andRGBW LED 314; for RGBW LED 312 and RGBW LED 316; for RGBW LED 318 andRGBW LED 322; and for RGBW LED 320 and RGBW LED 324. Advantageously, thelight pattern of the multispectral light sources 310-324 can be moresquare and uniform, as compared to conventional lighting systems,because the color LED dies 326-332 are covering each quadrant andbecause the lighting positions of the differently colored LEDs, withinthe larger LED dies, are collectively balanced.

In other embodiments, each possible color LED die orientation may beprovided in each quadrant. In yet another embodiment, the illuminationsystem includes four multispectral light sources (and, therefore, fourmultispectral light assemblies) and one multispectral light source islocated in each quadrant. In this latter embodiment, for example, thered LED die of each multispectral light source may be located at eachcorner of each quadrant to provide symmetry. Further, although theillustrated configuration of color LED dies can be advantageous,including for reasons discussed above, other configurations are alsopossible.

In some embodiments, various combinations of the multispectral lightassemblies may be activated to provide the illumination light. FIG. 4illustrates example illumination light patterns generated using variouscombinations of illumination from multispectral light assemblies in anillumination system in accordance with an embodiment of the technology.The example illumination system used to generate the illumination lightpatters shown in FIG. 4 includes eight multispectral light sources410-424 (and the associated multispectral light assemblies) that arepositioned symmetrically around a camera axis. For this example, themultispectral light sources were RGBW LEDs. A first illumination pattern440 was generated using a first north RGBW LED located in the firstquadrant. The remaining illumination patters 442-454 represent theillumination pattern generated by adding on an additional RGBW LED412-424, respectively, one at a time moving clockwise.

In this regard, it can be seen that the illumination pattern 442generated with the first north RGBW LED and second north RGBW LED 412has improved uniformity of the illumination as compared to theillumination pattern 440. However, image acquisition may still besub-optimal, including if the image sensor (e.g., image sensor 204 shownin FIG. 2 ) of the vision system is a linear sensor. For example, acentral area of the illumination pattern 442 generated by the north bankof RGBW LEDS 410, 412 may be of deficient intensity towards the bottomside of the central imaging area.

Continuing, the illumination pattern 446 was generated using four of theRGBW LEDS 410, 412, 414, and 416, has acceptable uniformity, however, itis not as bright as if all of the RGBW LEDS 410-424 are used to generatethe illumination as shown by illumination pattern 454. Thus, forexample, by utilizing all of the multi-spectral light sources 410-424,as shown via the illumination pattern 454, a bright, highly uniform,symmetrical, square pattern can be obtained. Accordingly, in someembodiments, different combinations of the multispectral light sourcemay be utilized to generate the illumination based on the requirementsof the application of the vision system. In some cases, a beneficialbalancing of light sources of different colors (e.g., as discussedrelative to FIG. 3 ) can be implemented in combination with theillumination strategy discussed relative to FIG. 4 , with particularlybeneficial results. However, other distributions of differently coloredillumination sources can also be used.

FIG. 5 is a schematic diagram showing example light bankingconfigurations of an illumination system in accordance with anembodiment of the technology. In some embodiments, different lightbanking configurations may be used to provide the illumination light fordifferent applications. For example, light banking configurations ofmultispectral light sources may be used for applications such as toprovide good lighting conditions for surface features detectionalgorithms such as, for example, surface FX feature extractiontechnology, to provide low angle light effect, or to provide color lightbanking. Advantageously, a set or array of multispectral light sources(e.g., RGBW LEDs) may be selected in different configurations (e.g., inNorth, South, East, and West quadrants). For example, selecting aparticular set (e.g., array) of LEDs in one or more particular quadrantsto generate the illumination (e.g., quadrants 302-308 shown in FIG. 3 )can provide benefits including uniformity within the quadrant, e.g., ifit is desirable to create shadows. In some embodiments, selectivecontrol of light banks can be implemented using multispectral lighting,as variously described herein. However, other lighting configurationsare also possible.

In FIG. 5 , six example light banking configurations are shown, as maycorrespond to control of lighting for six different image acquisitions(e.g., six different exposures). A first example configuration 502includes illumination of a bank of multispectral light sources 530 thatare positioned north of a camera axis 504 of the vision system. A secondexample configuration 506 includes illuminating the bank ofmultispectral light sources 530 and a bank of multispectral lightsources 532 positioned west of the camera axis 504 of the vision system.A third example configuration 510 includes illuminating the bank ofmultispectral light sources 532 and a bank of multispectral lightsources 534 positioned east of the camera axis 504 of the vision system.A fourth example configuration 514 includes illuminating the bank ofmultispectral light sources 530, the bank of multispectral light sources532 and a bank of multispectral light sources 536 positioned south ofthe camera axis 504 of the vision system. A fifth example configuration518 includes illuminating the bank of multispectral light sources 532,the bank of multispectral light sources 534, the bank of multispectrallight sources 534 and the bank of multispectral light sources 536. Asixth example configuration includes illuminating the bank ofmultispectral light sources 530 and the bank of multispectral lightsources 536. Although the illustrated light banking configurations canbe advantageous, other configurations are also possible.

In some embodiments, each bank of multispectral light sources (e.g., the“north” bank (or quadrant) 530, the “west” bank (or quadrant) 532, the“east” bank (or quadrant) 534, and the “south” bank (or quadrant) 536shown in FIG. 5 ) may be used to provide illumination in one of thecolors of the LED's included in each multispectral light source in thebank. For example in the second example configuration 506, a red LED ofeach multispectral light source in the “north” bank 530 may be activatedto provide red illumination light from the “north” bank 530 and a greenLED of each multispectral light source in the “west” bank 532 may beactivated to provide green illumination light from the “west” bank 532In another example, in the fourth example configuration 514, a green LEDof each multispectral light source in the “north” bank 530 may beactivated to provide green illumination light from the “north” bank 530,a blue LED of each multispectral light source in the “west” bank 532 maybe activated to provide blue illumination light from the “west” bank532, and a red LED of each multispectral light source in the “south”bank 536 may be activated to provide red illumination light from the“south” bank 536. In some embodiments, two or more banks ofmultispectral lights may be used to provide the same color illuminationlight. During operation of the illumination system, the color of theillumination light provided by a bank of multispectral light sources maybe changed by changing the color LED activated in each multispectrallight source. For example, the “north” bank 530 may be changed from ared illumination light to a blue illumination light by changing the LEDactivated in each multispectral light source of the “north” bank 530from a red LED to a blue LED.

FIG. 6 illustrates a method for controlling an illumination system withmultispectral light assemblies for generating an image in accordancewith an embodiment of the technology. As mentioned above with respect toFIG. 2 , the amount of light from the different color channels generatedby the multispectral light assemblies in the illumination system may becontrolled using an illumination sensor (e.g., illumination sensor 222shown in FIG. 2 ) and a processor (e.g., processor 202 shown in FIG. 2 )to form a feedback loop. In some embodiments, the color channels areadvantageously activated sequentially. For example, a separate exposuremay be used for each sequentially activated color channel or each colorchannel can be activated sequentially during the same single exposure.

In one example, at block 602, a first color illumination light beam isprojected onto an object by activating, for example, a correspondingcolor LED die of one or more multispectral light assemblies (e.g.,multispectral light assembly 100 shown in FIG. 1 ). In some embodiments,the light beam may be a single color (e.g., may be generated by onlyLEDs of a single color). At block 604, the intensity of the generatedcolor illumination light beam is measured using an illumination sensor(e.g., illumination sensor 222 shown in FIG. 2 ). For example, part ofthe color illumination light transmitted from one more multispectrallight assemblies can be diverted onto the illumination sensor that thenmeasures the intensity of the light. In some embodiments, theillumination sensor may be a photo-diode, which may not be particularlytuned to any given color of light.

At block 606, it is determined (e.g., by a processor device) whether themeasured intensity is sufficient, e.g., whether the measured intensitygenerates a target exposure or amount of light (i.e., the product of themeasured intensity and the exposure time) or whether the integratedintensity for the color over a particular time (e.g., within the currentexposure) is sufficient. If the measured intensity at block 604 is notsufficient to generate the target exposure, the amount of light (e.g.,intensity or duration of illumination of the color LED die(s)) isadjusted at block 608. Or, if the total intensity over time is notsufficient, a length of an exposure for that color of light may beadjusted (e.g., extended). In some embodiments, the intensity of thelight beam will continue to be measured, and corresponding adjustmentsmade, until the intensity is sufficient (e.g., the current intensity orthe intensity over time generates the target exposure (or amount oflight)).

In some embodiments, as also noted above, adjusting an amount of light(e.g., at block 608) can include adjusting a duration of an amount oftime during which a particular color of light is used to illuminate atarget. For example, during an image acquisition over a single ormultiple exposures, the duration of illumination for any given color oflight from a multispectral illumination assembly can be determined inreal time (or otherwise) by monitoring the cumulative illuminationprovided by that color of light and determining when the cumulativeillumination is sufficient for good image acquisition.

Once the intensity of the color illumination light beam reaches thetarget intensity (or target exposure) at block 606, it is determinewhether there are any additional color illuminations (e.g., colorchannels) that need to be projected on the object at block 610. Thespecific color channels that are projected on the object may bedetermined, for example, based on the specific application of the visionsystem. If there is an additional color illumination at block 610, thefirst color illumination light beam can be turned off and a second colorillumination light beam (or color channel) is projected in the object atblock 612 and the process move to block 604. At block 604, the intensityof the second generated color illumination light beam is measured usingthe illumination sensor (e.g., illumination sensor 222 shown in FIG. 2). The amount of light from second color illumination light beam is thenadjusted at block 608 until it reaches the target intensity (or targetexposure) at block 610.

Blocks 604-612 can be repeated, as appropriate, for each colorillumination light beam, for example for N color illumination lightbeams, until all of the color channels have been projected at the targetintensity (or target exposure). As mentioned above, the color channelsmay sometimes thus be activated sequentially, and in some cases a priorcolor channel can be turned off before the next color channel is turnedon.

As the various color illumination light beams (or color channels) areprojected on the object, the illumination light reflected from theobject is received by the vision system and, for example, directed to animage sensor by one or more lenses at block 614 (e.g., images sensor 204and lens(es) 208 shown in FIG. 2 ). Once all of the necessary colorillumination light beams (or color channels) have been projected atblock 610, one or more images of the object or a symbol on the objectmay be generated based on the received illumination light using aprocessor (e.g., processor 202 shown in FIG. 2 ) at block 616. Knownmethods may be used for generating an image of the object or a symbol onthe object and deciding data therein. For example, a single image can begenerated based on a single exposure, during which different colors oflight illuminate an object at different times, or a single image can begenerated as a composite of multiple exposures, during which differentcolors of light are used.

As mentioned above, it may be advantageous to activate each colorchannel sequentially so that only one channel is on at any time.Accordingly, in some embodiments, the illumination sensor only needs tomeasure one color channel at a time and the illumination sensor may be,for example, a single photo-diode that may be used to measure each ofthe color channels.

As mentioned above, in some embodiments a separate exposure may be usedfor each sequentially activated color channel. FIG. 7 is a graphillustrating a timing configuration using multiple exposures forgenerating an image using an illumination system with multispectrallight assemblies in accordance with an embodiment of the technology. Theexample timing configuration 700 includes three separate exposures,namely, a first exposure 702, a second exposure 704 and a third exposure706 that occur sequentially over time as illustrated by axis 714. Afirst color channel 708 (e.g., red) may be activated and may be used togenerate illumination light during the first exposure 702. At thecompletion of the first exposure 702, the first color channel 708 may beturned off and a second color channel 710 (e.g., green) may be activatedand may be used to generate illumination light during the secondexposure 704. At the completion of the second exposure 704, the secondcolor channel 710 may be turned off and a third color channel 712 (e.g.,blue) may be activated and may be used to generate illumination lightduring the third exposure 706. Each exposure may be used to generate amonochromatic image. The monochromatic images from the three differentcolor channels may then be merged to create a full RGB (or other) image.Known methods may be used for creating a full RGB image from a pluralityof monochromatic images. In some embodiments, the duration of theexposures 702, 704, 706 can be determined according to the methodillustrated in FIG. 6 , or as otherwise generally discussed above.

In some embodiments, each color channel can be activated sequentiallyduring the same exposure. FIG. 8 is a graph illustrating a timingconfiguration using a single exposure for generating an image using anillumination system with multispectral light assemblies in accordancewith an embodiment of the technology. The example timing configuration800 includes a single exposure 802. Each color channel may be activatedsequentially over time during the exposure 802 as illustrated by axis810. A first color channel 804 (e.g., red) may be activated at a firsttime point and may be used to generate illumination light during theexposure 802. At the completion of a particular time period foractivation of the first color channel 804, the first color channel 804may be turned off and a second color channel 806 (e.g., green) may beactivated at a second time point and may be used to generateillumination light during the exposure 802. At the completion of aparticular time period for activation of the second color channel 806,the second color channel 806 may be turned off and a third color channel808 (e.g., blue) may be activated at a third time point and may be usedto generate illumination light during the exposure 802. The third colorchannel 808 may be activated for a particular period of time and thenturned off. Thus, the three color channels 804, 806 and 810 may be mixedduring the exposure 802 without actually overlapping in time. Asdescribed above with respect to FIG. 6 , an illumination sensor andfeedback loop may be used to control the intensity and/or the on-time ofeach channel 804, 806, 808 (i.e., the width of the pulses for each colorchannel along the axis 810) to achieve the correct color mix.Accordingly, the color mixing may be controlled during a single exposuretime of the camera of the vision system. The single exposure may be usedto generate a monochrome image according to any variety of knownmethods. However, the monochrome image may advantageously have optimizedcontrast for one or more of the associated colors. Further, because asingle exposure can be faster than multiple separate exposures, whileproviding a comparable cumulative lighting intensity, the timingconfiguration of FIG. 8 may be advantageous for sorting applicationsthat involve moving objects.

As mentioned above, in some embodiments, each wavelength or colorchannel may be activated simultaneously so that multiple channels are on(i.e., illuminating a target for imaging) at the same time. Accordingly,in some embodiments, the illuminations sensor may include a plurality ofillumination sensors and each illumination sensor may be configured tomeasure one of the color channels. For example, each illumination sensormay be, for example, a photodiode configured to measure one of thecolors. In some embodiments, for simultaneous illumination with aplurality of colors channels, the illumination sensor may be a singleillumination sensor (e.g., a photodiode) configured to measure all ofthe color channels simultaneously. As mentioned above, the intensity oran exposure time of each color channel can be adjusted until a targetamount of light or exposure (i.e., the product of the intensity andexposure duration (or exposure time or LED on-time)) is reached. Oncethe target exposure (or amount of light) is reached for a particularcolor channel, the channel can be turned off.

In some embodiments, the vision system 200 may be used with a removablediffused light assembly mounted to a housing of the vision system infront of the illumination assembly to enable the vision system toconvert the illumination light to diffuse light provided at shorterdistances. Accordingly, the diffused light assembly can enable thevision system 200 with multispectral light assemblies to be used withapplications that require diffuse light and shorter working distances.The diffused light assembly may be advantageous for imaging forapplications such as direct part marking (DPM), as well as otherapplications that require diffuse light. A DPM reader is capable ofreading barcodes that are etched or imprinted directly onto the surfaceof materials such as plastics and metals. Typically, DPM parts presentcodes on a larger variety of geometries and surfaces.

FIG. 9 illustrates an example diffused light assembly in accordance withan embodiment of the technology. In the embodiment illustrated in FIG. 9, a removable diffused light assembly 900 includes a housing 902 and aninternal reflective surface 904. In an embodiment, the internalreflective surface 904 may include a matte white surface to assist thelight traveling inside the volume of the diffused light assembly 900.Dimensions of the housing 902 (depth 906, height 908 and width 910) maybe configured to allow the diffused light assembly 900 to be removablymounted to the housing of a vision system (e.g., vision system 200 shownin FIG. 2 ) so that the diffused light assembly 900 may be positioned infront of the vision system illumination assembly. In some embodiments,the height (H) 908 of the housing 902 is half the FOV at the neardistance. The housing of the vision system may also be configured toinclude features to allow the diffused light assembly 900 to be attachedto the vision system. Although the illustrated arrangement of thediffused light assembly 900 can be advantageous, including for reasonsdiscussed above, other configurations are also possible.

FIG. 10 is a schematic diagram of a vision system and a diffused lightassembly (e.g., similar to the assembly 900 of FIG. 9 ) in accordancewith an embodiment of the technology. In FIG. 10 , a diffused lightassembly 1000 may be removable mounted or attached to a visions system1022. For example, a housing 1002 of the diffused light assembly 1000may be attached to a housing 1024 of the vision system using amechanical attachment mechanism at a mechanical connection point 1020.Known mechanical attachment mechanisms may be used to removably attachthe housing 1002 of the diffused light assembly 1000 to the housing ofthe vision system 1024. As mentioned above, the diffused light assembly1000 may be attached to the vision system housing 1024 so that thediffused light assembly 1000 is positioned in front of an illuminationassembly 1018 of the visions system 1022 (e.g., a multispectralillumination assembly, as generally described above). In someembodiments, the diffused light assembly 1000 may be a passive accessorythat does not require electrical connections or additional communicationwith a camera of the visions system 1022. Vision system 1022 may alsoinclude an image sensor 1014 and lens(es) 1016, in addition to othercomponents used to image a symbol or ID on an object.

In the illustrated embodiment, diffused light assembly 1000 includes ahousing 1002 that has an internal reflective surface 1012 (e.g.,internal reflective surface 904 shown in FIG. 9 ) and also includes adiffuser 1004. In some embodiments, the diffuser may be formed from amaterial (e.g., a milky white material) for which both translucency andtexture may be defined to deliver light in the desired manner. Thediffuser 1004 can provide an aperture in front of the imaging lens(es)1016 of the vision system 1022. In some embodiments, the size of theaperture may be optimized to create the minimum impact on the evenillumination produced by the diffused light assembly 1000. The diffusedlight assembly can be configured to create the effect of a dome lightbetween the internal reflective surface 1012 and the diffuser 1004.Advantageously, the removable diffused light assembly may be used withdifferent lenses (FOVs), illumination beams, light banks, and colors.The diffused light assembly 1000 can improve performance by providing auniform light pattern for every position of the focus plane over acertain working range (e.g., 0-100 mm for factory automation DMapplications). Although the illustrated arrangement of the diffusedlight assembly 1000 can be advantageous, including for reasons discussedabove, other configurations are also possible.

The foregoing has been a detailed description of illustrativeembodiments of the technology. Various modifications and additions canbe made without departing from the spirit and scope of this disclosure.Features of each of the various embodiments described above may becombined with features of other described embodiments as appropriate inorder to provide a multiplicity of feature combinations in associatednew embodiments. Furthermore, while the foregoing describes a number ofseparate embodiments of the apparatus and method of the presentdisclosure, what has been described herein is merely illustrative of theapplication of the principles of the present disclosure. Also, as usedherein various directional and orientation terms such as “vertical”,“horizontal”, “up”, “down”, “bottom”, “top”, “side”, “front”, “rear”,“left”, “right”, and the like are used only as relative conventions andnot as absolute orientations with respect to a fixed coordinate system,such as gravity. Accordingly, the description is meant to be taken onlyby way of example, and not to otherwise limit the scope of thisdisclosure.

In some embodiments, aspects of the technology, including computerizedimplementations of methods according to the technology, can beimplemented as a system, method, apparatus, or article of manufactureusing standard programming or engineering techniques to producesoftware, firmware, hardware, or any combination thereof to control aprocessor device (e.g., a serial or parallel general purpose orspecialized processor chip, a single- or multi-core chip, amicroprocessor, a field programmable gate array, any variety ofcombinations of a control unit, arithmetic logic unit, and processorregister, and so on), a computer (e.g., a processor device operativelycoupled to a memory), or another electronically operated controller toimplement aspects detailed herein. Accordingly, for example, embodimentsof the technology can be implemented as a set of instructions, tangiblyembodied on a non-transitory computer-readable media, such that aprocessor device can implement the instructions based upon reading theinstructions from the computer-readable media. Some embodiments of thetechnology can include (or utilize) a control device such as anautomation device, a special purpose or general purpose computerincluding various computer hardware, software, firmware, and so on,consistent with the discussion below. As specific examples, a controldevice can include a processor, a microcontroller, a field-programmablegate array, a programmable logic controller, logic gates etc., and othertypical components that are known in the art for implementation ofappropriate functionality (e.g., memory, communication systems, powersources, user interfaces and other inputs, etc.).

The term “article of manufacture” as used herein is intended toencompass a computer program accessible from any computer-readabledevice, carrier (e.g., non-transitory signals), or media (e.g.,non-transitory media). For example, computer-readable media can includebut are not limited to magnetic storage devices (e.g., hard disk, floppydisk, magnetic strips, and so on), optical disks (e.g., compact disk(CD), digital versatile disk (DVD), and so on), smart cards, and flashmemory devices (e.g., card, stick, and so on). Additionally it should beappreciated that a carrier wave can be employed to carrycomputer-readable electronic data such as those used in transmitting andreceiving electronic mail or in accessing a network such as the Internetor a local area network (LAN). Those skilled in the art will recognizethat many modifications may be made to these configurations withoutdeparting from the scope or spirit of the claimed subject matter.

Certain operations of methods according to the technology, or of systemsexecuting those methods, may be represented schematically in the FIGS.or otherwise discussed herein. Unless otherwise specified or limited,representation in the FIGS. of particular operations in particularspatial order may not necessarily require those operations to beexecuted in a particular sequence corresponding to the particularspatial order. Correspondingly, certain operations represented in theFIGS., or otherwise disclosed herein, can be executed in differentorders than are expressly illustrated or described, as appropriate forparticular embodiments of the technology. Further, in some embodiments,certain operations can be executed in parallel, including by dedicatedparallel processing devices, or separate computing devices configured tointeroperate as part of a large system.

As used herein in the context of computer implementation, unlessotherwise specified or limited, the terms “component,” “system,”“module,” and the like are intended to encompass part or all ofcomputer-related systems that include hardware, software, a combinationof hardware and software, or software in execution. For example, acomponent may be, but is not limited to being, a processor device, aprocess being executed (or executable) by a processor device, an object,an executable, a thread of execution, a computer program, or a computer.By way of illustration, both an application running on a computer andthe computer can be a component. One or more components (or system,module, and so on) may reside within a process or thread of execution,may be localized on one computer, may be distributed between two or morecomputers or other processor devices, or may be included within anothercomponent (or system, module, and so on).

1. An illumination assembly for a machine vision system, theillumination system comprising: a plurality of multispectral lightassemblies, each multispectral light assembly of the plurality ofmultispectral light assemblies comprising: a multispectral light sourceconfigured to generate a plurality of different wavelengths of light; alight pipe having an entrance surface and an exit surface and positionedin front of the multispectral light source, relative to an illuminationdirection, the light pipe configured to receive two or more of theplurality of different wavelengths of light generated by themultispectral light source and to provide color mixing for the two ormore of the plurality of different wavelengths of light; a diffusivesurface on the exit surface of the light pipe and configured to receivecolor-mixed light transmitted from the light pipe; and a projection lenspositioned in front of the diffusive surface and configured to receivethe color-mixed light from the diffusive surface and to project a lightbeam onto an object that include the color-mixed light; and a processordevice in communication with the plurality of multispectral lightassemblies, the processor device being configured to control activationof the multispectral light source of each of the plurality ofmultispectral light assemblies.
 2. The illumination assembly accordingto claim 1, wherein the multispectral light source includes a pluralityof color light emitting diodes (LEDs), configured to separately providedifferent respective wavelengths of light.
 3. The illumination assemblyaccording to claim 2, wherein the multispectral light source is one ofan RGBW LED, an RGB IR LED, or an RGBY LED.
 4. The illumination assemblyaccording to claim 1, further comprising an illumination sensor incommunication with the processor device and configured to receive atleast one wavelength of light generated by the multispectral lightsource and measure the intensity of the wavelength of light.
 5. Theillumination assembly according to claim 4, wherein the processor deviceis configured to receive the measured intensity of the at least onewavelength of light and one or more of adjust the intensity of the atleast one wavelength of light or adjust an exposure time for the atleast one wavelength of light, based on the measured intensity.
 6. Theillumination assembly according to claim 5, wherein the processor deviceis configured to adjust the intensity of the at least one wavelength oflight based on comparing the measured intensity to a target intensity.7. The illumination assembly according to claim 1, wherein the diffusivesurface is configured to control an angle of the light transmitted fromthe light pipe.
 8. The illumination assembly according to claim 7,wherein the diffusive surface is configured to control the shape of thelight transmitted from the light pipe.
 9. The illumination assemblyaccording to claim 8, wherein the projection lens is one of anaspherical shaped lens, a spherical shaped lens, a toroidal shaped lens,a cylindrical shaped lens, a freeform shaped lens, or a combination oflens shapes.
 10. The illumination assembly according to claim 8, whereinthe light beam projected onto the object has a shape approximately equalto a shape of a field of view (FOV) of the machine vision system. 11.The illumination assembly according to claim 10, wherein the light beamprojected onto the object has a rectangular shape.
 12. The illuminationassembly according to claim 1, wherein the diffusive surface is aholographic diffuser positioned on the exit surface of the light pipe.13. The illumination system according to claim 1, wherein the diffusivesurface is a diffusing texture on the exit surface of the light pipe.14. The illumination assembly according to claim 1, wherein a shape ofthe light pipe and a ratio between an area of the entrance surface andthe exit surface of the light pipe are optimized for color mixing.
 15. Amachine vision system comprising: an optics assembly with at least onelens; a sensor assembly including an image sensor; an illuminationassembly comprising a plurality of multispectral light assembliespositioned symmetrically around the at least one lens, wherein eachmultispectral light assembly of the plurality of multispectral lightassemblies comprises: a multispectral light source having a plurality ofcolor LED dies, wherein each of the plurality of color LED diesgenerates a different respective wavelength of light and wherein anorientation of the plurality of color LED dies is configured to providea balanced distribution of color in an illumination area; a light pipepositioned in front of the multispectral light source, the light pipehaving an exit surface; a diffusive surface on the exit surface of thelight pipe; and a projection lens positioned in front of the diffusivesurface and configured to project the illumination area onto an object;and a processor device in communication with the optics assembly, thesensor assembly and the illumination assembly, the processor devicebeing configured to control activation of each of the plurality of colorLED dies.
 16. The machine vision system according to claim 15, whereinthe processor device is configured to activate each of the plurality ofcolor LED dies sequentially.
 17. The machine vision system according toclaim 16, wherein the processor device is configured to activate each ofthe plurality of color LED dies sequentially during a single exposuretime.
 18. The machine vision system according to claim 15, furthercomprising: a housing disposed around the optics assembly, the sensorassembly, the illumination assembly and the processor device; and adiffused light assembly removably attached to the housing in front ofthe illumination assembly, the diffused light assembly configured toconvert light transmitted from the illumination assembly to a diffuselight.
 19. The machine vision system according to claim 15, wherein eachLED die of the plurality of color LED dies includes a plurality oflighting positions, with each lighting position of the plurality oflighting positions for each LED die of the plurality of color LED diesincluding an LED of a different respective color; and wherein theplurality of multispectral light assemblies collectively include anequal number of the different respective colors in each of the pluralityof lighting positions.
 20. A method for controlling an illuminationsystem for a machine vision system used to acquire an image of a symbolon an object, the method comprising: projecting, using at least onemultispectral light source and a corresponding light pipe, a first lightbeam for a first period of time, the first light beam having a firstwavelength associated with a first color channel; measuring, using anillumination sensor, an intensity of the first light beam; comparing,using a processor device, the measured intensity of the first light beamto a first target intensity; adjusting, using the processor device, anamount of light for the first light beam based on the comparison of themeasured intensity of the first light beam and the target intensity,until the measured intensity of the first light beam is equal to thetarget intensity; after the first period of time, projecting, using theat least one multispectral light source and a corresponding light pipe,a second light beam for a second period of time, the second light beamhaving a second wavelength associated with a second color channel;measuring, using the illumination sensor, an intensity of the secondlight beam; comparing, using the processor device, the measuredintensity of the second light beam to a second target intensity;adjusting, using the processor device, an amount of light for the secondlight beam based on the comparison of the measured intensity of thesecond light beam and the second target intensity, until the measuredintensity of the second light beam is equal to the second targetintensity.
 21. The method according to claim 20, wherein the first lightbeam and the second light beam are projected sequentially.
 22. Themethod according to claim 21, wherein the first period of time and thesecond period of time are within one exposure time.
 23. The methodaccording to claim 21, wherein adjusting the amount of light for thefirst light beam or the second light beam includes adjusting theduration of the first period of time or the second period of time.